Throughout the business world, inkjet printing systems are extensively used for image reproduction. Inkjet printing systems frequently make use of an inkjet printhead mounted within a carriage that is moved back and forth across print media, such as paper. As the printhead is moved across the print media, a control system activates the printhead to deposit or eject ink droplets onto the print media to form images and text. Such systems may be used in a wide variety of applications, including computer printers, plotters, copiers, facsimile machines, and other printing devices.
Ink is provided to the printhead by a supply of ink that is either carried by the carriage or mounted to the printing system such that the supply of ink does not move with the carriage. For the case where the ink supply is not carried with the carriage, the ink supply can be in fluid communication with the printhead to the ink supply is connected whereupon the printhead is replenished with ink from the refilling station.
For the case where the ink supply is carried with the carriage, the ink supply may be integral with the printhead whereupon the entire printhead and ink supply is replaced when ink is exhausted. Alternatively, the ink supply can be carried with the carriage and be separately replaceable from the printhead.
For convenience, the concepts of the invention are discussed in the context of thermal inkjet printheads. A thermal inkjet printhead die includes an array of firing chambers having orifices (also called nozzles) which face the print media. The ink is applied to individually addressable ink energizing or ejecting elements (such as firing resistors) within the firing chambers. Energy provided by the firing resistors heats the ink within the firing chambers causing the ink to bubble. This in turn causes the ink to be expelled out of the orifice of the firing chamber toward the print media. As the ink is expelled, the bubble collapses and more ink is drawn into the firing chambers, allowing for repetition of the ink expulsion process.
Inkjet printhead dies are in part manufactured using processes that employ photolithographic techniques similar to those used in semiconductor manufacturing. The components are constructed on a flat substrate layer of silicon by selectively adding layers of various materials and subtracting portions of the substrate layer and added layers using these photolithographic techniques. Some existing inkjet printhead dies are defined by a silicon substrate layer having firing resistors within a stack of thin film layers, a barrier layer and an orifice layer or orifice plate. Material removed from the barrier layer defines the firing chambers, while openings within the orifice layer or plate define the nozzles for the firing chambers.
In an inkjet printhead die, ink is delivered to the firing chambers and thereby the firing resistors by either a slotted ink delivery system or an edgefeed ink delivery system. In a slotted ink delivery system, the inkjet printhead die includes one or more slots that route ink from a backside of the printhead die to a front side where the firing resistors reside on at least one side of each of the slots. To form the ink feed slots of the printhead die, material is typically removed from the silicon substrate layer by directing a high pressure mixture of sand and air at the silicon substrate layer.
Generally, a single color printhead die includes a single ink delivery slot with one column of firing resistors on each side of the slot. However, a single color printhead die may include multiple slots to improve print quality and/or speed. A multicolor printhead die typically includes an ink delivery slot for each color. Generally, the printhead die is mounted to a printhead cartridge body using a structural adhesive. In multicolor print cartridges having a printhead die with multiple slots, this structural adhesive is deposited in a loop around each individual slot to separate out the individual ink colors.
Although this slotted ink delivery system for inkjet printhead dies adequately delivers ink to the firing resistors, there are some disadvantages to this system of ink routing. The primary disadvantages are die strength, size and manufacturing inefficiencies. With regard to strength, in a printhead die, the ink delivery slot(s) structurally weaken the printhead die. As such, the greater the size of the slots and/or the greater the number of slots the weaker the die. With regard to size, the ink delivery slots can only be put so close together before manufacturability issues arise that causes manufacture of the printhead die to be accomplished in less than an optimal cost efficient manner. As such, the width of the ink delivery slots and the spacing of the ink delivery slots limits how small the printhead die can be. Lastly with regard to manufacturing inefficiencies, use of the high pressure mixture of sand and air to form the ink feed slots in the printhead die limits the overall size of the individual slots. For example, to produce an ink delivery slot having a width of less than 300 xcexcm and a length greater than 5000 xcexcm can require huge increases in manufacturing cycle times along with reductions in manufacturing yields. As such, due to the inherent limitations of the high pressure sand and air ink feed slot formation process, this process is only economically feasible to produce ink feed slots having widths of greater than 300 xcexcm and lengths less than 5000 xcexcm.
Typically to obtain print quality and speed, it is necessary to maximize the density of the firing chambers (i.e. firing resistors) and/or increase the number of firing chambers. Maximizing the density of the firing chambers and/or increasing the number of firing chambers typically necessitates an increase in the size of the printhead die and/or a miniaturization of printhead die components. As discussed above, when the density is sufficiently high, conventional manufacturing by assembling separately produced components becomes more difficult and costly. In addition, the substrate that supports firing resistors, the barrier that isolates individual resistors, and the orifice plate that provides a nozzle above each resistor are all subject to small dimensional variations that can accumulate to limit miniaturization. Further, the assembly of such components for conventional printheads requires precision that limits manufacturing efficiency.
As such, there is a desire to form improved slotted substrates that can be incorporated into various fluid ejecting devices and printing devices. An example of which can be a printhead die employing a slotted ink delivery system that is economical to manufacture, and relatively simple to incorporate into inkjet printhead cartridges useable in thermal inkjet printing systems. In particular, the printhead die and the process for manufacturing the printhead die should allow the formation of ink feed slots having widths less than 300 xcexcm and/or lengths greater than 5000 xcexcm while maintaining manufacturing efficiencies. Moreover, the printhead die and the process for manufacturing the printhead die should allow an overall reduction in the size of the printhead die while maintaining the same number of firing resistors or allow more firing resistors to be included in the same printhead die size.